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Nd. 228,730. Patented June 15,1880.

N PETERS, PHOTO-LITHOGRAPMER, wAsNlNGTON, D Q

- UNITED STATES PATENT OFFICE.

ROBERT A. COIT, OF NEW YORK, N. Y.

LAM P-CAP.

SPECIFICATION forming part of Letters Patent No. 228,730, dated June 15, 1880.

Application filed January 6, 1880.

To all whom it may concern Be it known that I, ROBERT A. UOIT, of New York, in the county and State of New York, have invented a certain new and useful Improvement in Lamp-Caps, of which the following is a specification.

This device consists'of a sheet-metal cap having an internal screw-thread fitting a male thread, which is formed on a sheet-metal collar to be applied to a lamp of glass or other material, the said collar having a beveled rim projecting upward within an annular recess of the cap and a downturned internal flange, which will engage over and protect the margin of the orifice in the glass.

In the accompanying drawings, Figure 1 is a perspective view of the sheet-metal screwcap. Fig. 2 is a perspective view of the sheetmetal screw-collar on which it fits. Fig. 3 is a vertical section of the cap. Fig. 4 is a vertical section of the collar. Fig. 5 is a vertical section of the cap and collar united and attached to a lamp-body, shown in part section.

The sheet-metal cap A is stamped out with a screw-threaded flange or neck, a, surmounted by an external bead, b, preferably milled, as shown in Fig. 1, to facilitate turning it. Within the bead b, on the interior of the top of the cap, is an annular recess, 0, within this an annular groove, (1, and in the central part an internal convexity, e, for purposes presently to be explained, the sheet-metal cap being formed on the exterior with a concavity, e, to produce the internal convex center, e, and with an external annular rim, d, produced by the inter-.

within the thread a of the cap, a beveled shoulder, g, forming with the annular recess 0 a chamber for the purpose of receiving and retaining overflowing oil or gas and sealing the orifice and collar, a vertical annular bead, h, to fit within the annular groove d, and a downturned annular flange, i, which engages over the margin of the orifice in the glass, porcelain, or other material of the lamp L, (a part of which is shown in Fig. 5,) so as to protect it from injury. The internal flange, i, also forms a seat for the internal boss or convexity, e, in the center of the cap, the whole forming atightjoint either with or without packing.

Having thus described my invention, what I claim as new therein, and desire to secure by Letters Patent, is-- 1. The sheet-metal screw-cap A, constructed with annular recess 0, annular groove cl, and internal boss or convexity, e, as and for the purpose set forth.

2. The combination of the sheet-metal collar F, formed with a screw-thread, and beveled shoulder g, and the sheet-metal screwcap A, constructed with annular recess a and.

annular groove (1, as and for the purpose set forth.

ROBT. A. 0011. \Vitnesses:

WM. NELsoN URoMwELL, O. T. ARTHUR. 

